Studies worldwide have found that with each passing decade of their lives and with each insult they inflict on their bodies, men’s fertility decreases, while genetic risk to offspring slowly mounts. The range of findings is staggering: Several studies have shown that the older the man, the more fragmented the DNA in his ejaculated sperm, resulting in greater risk for infertility, miscarriage or birth defects. Investigations out of Israel, Europe, and the United States have shown that non-verbal (performance) intelligence may decline exclusively due to greater paternal age; that up to a third of all cases of schizophrenia are linked to increasing paternal age; and that men 40 and older are nearly six times more likely to have offspring with autism than men under age 30. Other research shows that the risk of breast and prostate cancer in offspring increases with paternal age.
The biggest news—the father’s role in brain disorders—has come to light largely because of research from Israel, where birth records routinely include the age of the male parent. The first unsettling finding linked paternal age and schizophrenia.
“In our first study, looking at every pregnancy in Jerusalem from 1964 to 1976, we found that increased age in the father predicted increased cases of schizophrenia in the children,” explains Malaspina, who was on the team doing the work. “In our second study we found that when the cases arose from new mutations—not familial inheritance—it almost always could be traced to the genetics of the father. Somewhere between a quarter and a third of the cases could be explained only by the age of the father—a threefold risk linked to fathers older than 50 compared with those in their 20s.” Studies in Sweden and California produced almost identical results.